I did a little research on this for a previous post.From the end of your previous post:
We now know that life extends back about 3 billion years before the CE. Multicellular life begins well over a billion years before the CE. And we now know that many animal phyla originate prior to the CE.I'm curious whether there's a period after which we can say that no new phyla have appeared?
“I’m curious whether there’s a period after which we can say that no new phyla have appeared?”
—I’m not sure what the most recent phylum is. But I’d say that, essentially, by definition, the beginning of a phylum is not something that can occur very recently - or that could occur tomorrow. It’s a label that would be put on a group of life forms only after many speciation events.
An analogy to a phylum and how it forms might be a language family (such as the “Romance Languages” of Latin, French, Romanian, etc).
At best, the witnesses to the time of the beginning of Latin probably wouldn’t have seen it as the beginning of a new language, but instead as merely a variation of another language (probably Greek?). And even if someone did see it as the beginning of a new language (which is highly unlikely) they certainly wouldn’t have seen it as the beginning of a whole new family type of languages. And thus the beginning of a language family is also something that, essentially by definition, is something that could only have occurred long ago. It won’t happen today. And the time that we call the beginning of a language will always be a case of “retrospective coronation”. Anyone living at the time of the beginning of Latin would have looking at that start as just a population of people speaking barely any differently than other populations - we can look back and call that time the beginning of a new language (and new language family) only because of our position far in the future and knowing what occurred later.